In recent years, multifarious postage scales incorporating digital circuitry and microprocessors have been developed. These specialized postage scales are typically equipped with means of weighing packages including letters and parcels, and capable of combining the weight and the shipping rate information stored therein to determine the postage and other charges for shipment of the packages.
Many of the electronic scales are also equipped with means of displaying the weight of a package, along with the postage and other shipping charges during the weighing process. For aesthetic reasons, the display screens of such scales are compact and relatively small. As such, the amount of information displayed on one such screen is extremely limited.
The shipping cost for a package to be delivered to a destination is dependent upon not only the weight of the package, but also the particular carrier used, the destination zone, the class of shipment, and the selected service options. In the United States, carriers such as the United States Postal Service (USPS), United Parcel Service (UPS) and Federal Express each have independent, different postage rates and charges for different service options. For example, USPS has various rates for first, second and third mailing classes, parcel post service, priority mail service, book rate service, etc. UPS levies extra charges for service options such as Collect on Delivery (COD), Delivery Confirmation Response (DCR), Declared Value (DV) and the like.
Because of the existence of the many different carriers and their associated rates and charges, the amount of data to be stored in an electronic scale is substantial, and normally requires a dedicated memory in the form of a programmable read-only memory (PROM). However, whenever there is a change in the postage rates, or other cost factors, such memory needs to be replaced by an updated memory. The replacement undesirably calls for the service of a technician to disassemble the scale to physically remove the existing memory inside the scale.
Because of the many different rates and service options involved, the operating portion of an electronic postage scale normally includes many keys, each of which corresponds to a rate or a service option. The size of the operating portion is accordingly large and the presentation of the keys is confusing. The large keyboard would intimidate unskilled operators and leads to errors during a complicated operation. Attempts have been made to reduce the number of keys to simplify the operation. One such attempt involves use of special keys such as shift and/or control keys so that each key, coupled with the special keys, corresponds to two or more rates or service options. Nevertheless, such use of the special keys hardly reduces the complexity of the operation.